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Irrigation of rice fields can create excellent breeding sites for mosquitoes.
Source: Joerg Boethling/Still Pictures

The beginning of the latter half of the 20th century was marked by optimism about the conquest of infectious diseases. The discovery of antibiotics produced treatments for tuberculosis and other major infectious diseases, while insecticide use initially caused a decline in vector-borne diseases. Smallpox was eradicated and vaccines were developed for polio and other major childhood diseases. Fifty years later, due to the emergence of newly recognized infectious diseases and the re-emergence of known ones, optimism has been replaced by grave concern and, in some cases, dread (McMichael 2004, Institute of Medicine 1992 and 2001).

This growing concern in part reflects a recognition of the difficulties associated with preventing, controlling, or eradicating infectious diseases. Medical interventions have been unable to keep up with all infectious diseases because many disease-causing agents and vectors have developed resistance to available drugs and pesticides (Morens and others 2004, Singh and others 2004, WHO 1992). Resistance to antibiotics has been fostered by their overuse or misuse medically and in animal husbandry (Smith and others 2002, Horrigan and others 2002). In addition, the pace of vaccine and new drug development has been slower than anticipated, and the expense of new drugs has often limited their availability in developing countries. For many infectious diseases, such as malaria and dengue, vaccines are still not available.

These difficulties, along with the increasing evidence that environmental change is a major player and that effective environmental management may provide more cost-effective and sustainable control measures than using drugs and pesticides, suggest a need to refocus on potentially preventable environmental factors to reverse the trend of emergent and re-emergent infectious diseases (Chivian 2002, Patz and others 2004).

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